Science » Geomorphology and Sedimentation
The figure below is an example from the Tubbs Setback Restoration Project at the San Pablo Bay National Wildlife Refuge. The greatest sedimentation (average + standard error) occurred within the deep water channel, and the elevations of the outer and central areas of the project have converged to approximately 3.2 NAVD88 ft, despite a 91 cm difference in initial elevations. Data from the Nisqually Delta Restoration will be added after the restoration and updated annually.
Tidal creeks and channels are an important drainage and habitat feature of tidal salt marshes. They influence biological and physical characteristics such as plant and avian distributions, fish and invertebrate establishment, and soil biogeochemistry (Callaway et al. 2001, Zedler 2001, Hood 2006, Hood 2007). High-resolution low tide aerial photography, along with field surveys will be used to map changes in creek and channel development. We will use our integrated bathymetric system (Takekawa et al., submitted; Athearn et al., in press) consisting of a variable frequency acoustic profiler (Navisound 210; Reson, Inc., Slangerup, Denmark), real time kinematic global positioning system unit (RTK GPS; Leica Smartpole 1200), and laptop computer mounted on a shallow-draft, flat-bottom boat (Bass Hunter; Cabelas, Sidney, NE) to determine geomorphic characteristics. The echosounder determines water depth, while the RTK GPS determines location and elevation as the boat travels over inundated surfaces. Data are integrated and processed in SAS (SAS Institute 1999) and a bathymetric coverage will be generated in Geostatistical Analyst (ArcGIS; ESRI, Inc.). Annual sedimentation differences can be analyzed over surfaces using bathymetry maps and differences in elevations can be calculated in Geostatistical Analyst.
Permanent depth poles or sediment pins (Takekawa et al. 2002, Woo et al. 2007) will be placed across the marsh plain to measure sediment accretion or loss over time. Sedimentation pins (2” PVC pipe, schedule 40) will be installed throughout the project to capture subtidal (channel), mudflat, marsh, and upland habitat types. Sediment pins will be measured annually to examine the sedimentation rate. The pole will be surveyed to NAVD88 so that elevation of the sediment surface can be calculated by the pole height. As sediment accretes, the length of the exposed pole will decrease and vice versa. In addition, the characterization of sediment properties is critical for colonizing benthic invertebrates. We will gather soil samples annually and analyze for soil particle size, soil pH, organic matter content, and nutrients.